1. Field of the Invention
The present invention relates to magnetic memory devices, and more particularly to magnetic memory devices that have non-volatile memory arrays using magnetic tunnel resistive elements as the individual memory cells.
2. Description of the Background Art
A structure in which an insulative material is sandwiched between two ferromagnetic materials is called “magnetic tunnel junction (MTJ).”
FIG. 39 is a schematic diagram of a MTJ. In FIG. 39, an insulator layer TB is disposed between ferromagnetic layers FM1 and FM2. It is constructed so as to supply a terminal voltage to the ferromagnetic layers FM1 and FM2 via terminals T1 and T2, respectively. The resistance between the terminals T1 and T2 is referred to as “resistance of magnetic tunnel resistive element.”
When some measurements are made of the current tunneling through the insulator layer TB in this structure, there can observe the phenomenon that the current values are different, namely the resistances of magnetic tunnel resistive elements are different for different directions of the magnetization of the two ferromagnetic layers. In place of the insulator layer TB, a non-magnetic layer may be used.
This phenomenon is called “tunnel magnetic resistance (TMR) effect.”